Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.17 (lysozyme)
21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using X-ray coordinates of antigen-antibody complexes McPC 603, D1.3, and HyHEL-5, we made semiquantitative estimates of Gibbs free energy changes (delta G) accompanying noncovalent complex formation of the McPC 603 Fv fragment with phosphocholine and the D1.3 or HyHEL-5 Fv fragments with hen egg white lysozyme. Our empirical delta G function, which implicitly incorporates solvent effects, has the following components: hydrophobic force, solvent-modified electrostatics, changes in side-chain conformational entropy, translational/overall rotational entropy changes, and the dilutional (cratic) entropy term. The calculated delta G ranges matched the experimentally determined delta G of McPC 603 and D1.3 complexes and overestimated it (i.e., gave a more negative value) in the case of HyHEL-5. Relative delta G contributions of selected antibody residues, calculated for HyHEL-5 complexes, agreed with those determined independently in site-directed mutagenesis experiments. Analysis of delta G attribution in all three complexes indicated that only a small number of amino acids probably contribute actively to binding energetics. These form a subset of the total antigen-antibody contact surface. In the antibodies, the bottom part of the antigen binding cavity dominated the energetics of binding whereas in lysozyme, the energetically most important residues defined small (2.5-3 nm2) "energetic" epitopes. Thus, a concept of protein antigenicity emerges that involves the active, attractive contributions mediated by the energetic antigenic epitopes and the passive surface complementarity contributed by the surrounding contact area. The D1.3 energetic epitope of lysozyme involved Gly 22, Gly 117, and Gln 121; the HyHEL-5 epitope consisted of Arg 45 and Arg 68. These are also the essential antigenic residues determined experimentally. The above positions belong to the most protruding parts of the lysozyme surface, and their backbones are not exceptionally flexible. Least-squares analysis of six different antibody binding regions indicated that the geometry of the VH-VL interface beta-barrel is well conserved, giving no indication of significant changes in domain-domain contacts upon complex formation.
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PMID:On the attribution of binding energy in antigen-antibody complexes McPC 603, D1.3, and HyHEL-5. 247 71

Arginine 115 in the subsite F of human lysozyme (peptidoglycan N-acetylmuramoylhydrolase, EC 3.2.1.17) was replaced with lysine, histidine, glutamine or glutamine acid by site-directed mutagenesis. The conversions which conserve positive charge, Arg115 to Lys or His (at acidic pH), have little affected on either the kinetic parameters for Micrococcus lysodeikticus cells or the activity against glycol chitin, nor on the cleavage patterns of hexa(N-acetylglucosamine) [(GlcNAc)6] and penta(N-acetylglucosamine) [(GlcNAc)5]. On the other hand, the conversions which cause loss of the positive charge, Arg115 to His (neutral and alkaline pH), Gln or Glu, not only reduced the activity against glycol chitin but also changed the cleavage patterns for (GlcNAc)6 and (GlcNAc)5. These results suggest that Arg115 is structurally required not for the specific hydrogen bonding interaction with a sugar residue but for the positively charged character in the construction of subsite F in human lysozyme.
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PMID:A structural requirement in the subsite F of lysozyme. The role of arginine 115 in human lysozyme revealed by site-directed mutagenesis. 249 74

Soluble reduced lysozyme was extensively digested by a trypsin-like protease purified from the culture supernatant of the bacterium. The digestion peptides were separated and purified by reversed-phase high-performance liquid chromatography, and were subjected to amino acid analysis. The fragments were identified by their amino acid composition, and the cleavage sites in the lysozyme chain were determined. Like mammalian trypsin, the enzyme from B. gingivalis split peptide bonds non-specifically at carboxyl sides of internal arginine and lysine residues, but the lysine present at the amino terminus of the lysozyme chain was not released. In addition, the enzyme cleaved the peptide linkage at the amino side of lysine and bonds between leucine-glycine, alanine-leucine and leucine-serine. Thus the trypsin-like protease from B. gingivalis has some cleavage actions on lysozyme different from those of mammalian trypsin.
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PMID:Cleavage action of a trypsin-like protease from Bacteroides gingivalis 381 on reduced egg-white lysozyme. 251 80

In the absence of extracellular Ca2+, poly-L-arginine induces little lysozyme release from rabbit polymorphonuclear leukocytes (PMNs). The polycation causes plasma membrane damage, which is evident from the release of the cytoplasmic enzyme lactate dehydrogenase (LDH). In the presence of Ca2+ concentrations higher than 0.2 mM, poly-L-arginine induces a strong lysozyme release that is superimposed on the membrane-damaging effect. The results suggest that poly-L-arginine permeabilizes the plasma membrane, enabling Ca2+ to enter the cell, which results in the exocytotic release of granule constituents. The GTP analog GTP gamma S shifts the Ca2+ requirement of exocytosis to slightly higher concentrations, whereas it completely inhibits poly-L-arginine-induced LDH release. Pertussis toxin gives a moderate inhibition, and La3+ completely inhibits poly-L-arginine-induced enzyme release. Whereas poly-L-arginine alone induces little superoxide generation in rabbit PMNs, there is a synergistic enhancement of superoxide production when GTP gamma S and poly-L-arginine are present together. Guanine nucleotides apparently have a modulating effect on the actions of poly-L-arginine on the PMN, but the nature of this effect remains to be determined.
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PMID:Permeabilization and calcium-dependent activation of rabbit polymorphonuclear leukocytes by poly-L-arginine. 254 93

To elucidate the role of the proline residue in the engineered signal sequence that directs the secretion of human lysozyme in Saccharomyces cerevisiae, we have remodeled an idealized signal sequence L8 = Met-Arg-(Leu)8-Pro-Leu-Ala-Ala-Leu-Gly [Yamamoto, Y., Taniyama, Y., Kikuchi, M., & Ikehara, M. (1987) Biochem. Biophys. Res. Commun. 149, 431-436] in the vicinity of the proline residue. By analyzing the secretory capability of 10 engineered signal sequences, we have shown the following. (1) The proline residue is important for the secretion of human lysozyme and is allowed at position -4, -5, or -6. (2) The secretory capability of the engineered signal sequences is correlated with their predicted conformations. (3) The functional signal sequences that we have investigated can be generalized as follows: Met-Arg-(Leu)n-Pro-(Xaa)-Ala-Leu-Gly where n equals 6-12 and Xaa is Leu, Ala, or Leu-Ala or can be omitted.
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PMID:Important role of the proline residue in the signal sequence that directs the secretion of human lysozyme in Saccharomyces cerevisiae. 265 80

High-sensitivity scanning calorimetry has been employed to study the reversible thermal unfolding of the lysozyme of T4 bacteriophage and of its mutant form Arg 96----His in the pH range 1.80-2.84. The values for t1/2, the temperature of half-denaturation, in degrees Celsius and for the enthalpy of unfolding in kilocalories per mole are given by (standard deviations in parentheses) wild type t1/2 = 9.63 + 14.41 pH (+/- 0.58) delta Hcal = 5.97 + 2.33t (+/- 4.20) mutant form t1/2 = -19.84 + 21.31 pH (+/- 0.51) delta Hcal = -8.58 + 2.66t (+/- 4.48) At any temperature within the range -20 to 60 degrees C, the free energy of unfolding of the mutant form is more negative than that of the wild type by 3-5 kcal mol-1, indicating an apparent destabilization resulting from the arginine to histidine replacement. The ratio of the van't Hoff enthalpy to the calorimetric enthalpy deviates from unity, the value expected for a simple two-state process, by +/- 0.2 depending on the pH. It thus appears that the nature of the unfolding of T4 lysozyme varies with pH in unknown manner. This complication does not invalidate the values reported here for the temperature of half-completion of unfolding, the calorimetric enthalpy, the heat capacity change, or the free energy of unfolding.
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PMID:A scanning calorimetric study of the thermal denaturation of the lysozyme of phage T4 and the Arg 96----His mutant form thereof. 266 7

The structure of the temperature-sensitive mutant lysozyme of bacteriophage T4 in which arginine 96 is replaced by histidine has been determined crystallographically and refined to a residual of 17.6% at 1.9-A resolution. Overall, the three-dimensional structure of the mutant protein is extremely similar to that of wild type. There are local distortions in the mutant structure suggesting that the substituted His 96 residue is under strain. This appears to be one of the major reasons for the decreased thermostability. In wild-type lysozyme the guanidinium of Arg 96 is located at the carboxy terminus of alpha-helix 82-90 and makes a pair of hydrogen bonds to two of the carbonyl groups in the last turn of the helix. The loss of this "helix dipole" interaction also appears to contribute to the destabilization. The pKa* of His 96 in the mutant lysozyme has been determined by nuclear magnetic resonance and found to be 6.8 at 10 degrees C. This relatively normal value of the histidine pKa* suggests that the protonated and unprotonated forms of the imidazole ring are perturbed equally by the protein environment or, what is equivalent, the mutant lysozyme is equally stable with either histidine species.
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PMID:High-resolution structure of the temperature-sensitive mutant of phage lysozyme, Arg 96----His. 266 8

When recombinant ricin A chain transcripts are translated in a rabbit reticulocyte lysate the ribosomes are rapidly inactivated as shown by their inability to support translation of yeast preproalpha factor or chicken lysozyme transcripts added subsequently. In contrast, ribosomes which have translated transcripts encoding non-toxic polypeptides such as ricin B chain, readily translate the second transcript under identical conditions. Ribosome inactivation is accompanied by a highly specific modification of 28S rRNA which occurs at the same position as the N-glycosidic cleavage of an adenine residue and which is thought to cause inactivation of the ribosomes. Protein synthesis by wheat germ ribosomes was not inhibited under the conditions which inhibit reticulocyte ribosomes confirming earlier observations that plant cytoplasmic ribosomes are much less sensitive to inhibition by ricin A chain than are mammalian ribosomes. Using the same assay we have shown that deleting an internal hexapeptide, which shares homology with hamster elongation factor-2, completely abolishes catalytic activity. Deleting a second pentapeptide conserved between ricin A chain and the ribosome-inactivating plant toxin trichosanthin, had no effect. Deleting the first nine residues from the N-terminus of A chain did not affect toxicity whereas deleting a further three residues inactivated the polypeptide. Point mutations which individually converted arginine 48 and arginine 56 of ricin A chain to alanine residues or which deleted arginine 56 were also without effect on the catalytic activity of the toxin.
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PMID:Ribosome inactivation by ricin A chain: a sensitive method to assess the activity of wild-type and mutant polypeptides. 271 55

The quenching of the benzophenone triplet by lysozyme and its constituent amino acids in aqueous solutions have been studied. Native lysozyme quenches the benzophenone triplet with a high rate constant, 4 x 10(9) M-1 s-1. The quenching process takes place with production of significant amounts of free ketyl radicals, phi ketyl = 0.56, but with a very low benzophenone consumption yield (0.022). The consumption yield is considerably smaller than that observed for the free amino acids. This difference can be explained in terms of a dominant back hydrogen transfer to the protein in the disproportionation of the free radicals produced. Reduced and carboxymethylated lysozyme shows a higher quenching rate (7.8 x 10(9) M-1 s-1) and a larger benzophenone consumption yield (0.07). The deactivation of the benzophenone triplet by the native protein leads to its inactivation, with a quantum yield of 0.01. Tryptophan and arginine residues are destroyed with a quantum yield of 0.01. In the modified enzyme tyrosine and methionine groups are also consumed.
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PMID:Photointeraction of benzophenone triplet with lysozyme. 275 90

The secretory response of cytochalasin B-treated human polymorphonuclear neutrophils to the peptide chemoattractant f-Met-Leu-Phe (FMLP), the calcium ionophore A23187 and other secretagogues was measured by assaying neutrophil supernatants for the granular enzymes beta-glucuronidase and lysozyme. The dose-dependent enzyme secretion in response to 10(-8)-10(-4) M FMLP and A23187 was unaffected by pretreatment with 10-75 microM forskolin (an activator of adenylate cyclase), but inhibited by high concentrations of prostaglandins E1 and E2. The phosphodiesterase inhibitors isobutyl-methyl-xanthine (IBMX), papaverine and Ro 20-1724 dose dependently inhibited enzyme secretion from FMLP- or A23187-treated cells, and this effect was augmented in the presence of 50-75 microM forskolin. Similar results for PGE1, forskolin and forskolin/IBMX combinations were also obtained using leukotriene B4, platelet activating factor and C5a des-Arg as secretagogues. We conclude that the adenylate cyclase system of human neutrophils is activatable by forskolin, but that the regulatory effects of adenylate cyclase stimulants in these cells are greatly attenuated unless cyclic AMP-phosphodiesterases are inhibited. Thus the phosphodiesterase activity of neutrophils may be of functional importance and is relevant to the modulation of neutrophil activity in inflammation.
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PMID:Inhibition of human neutrophil degranulation by forskolin in the presence of phosphodiesterase inhibitors. 301 41


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